High frequency signal transmitter

ABSTRACT

The current invention provides a high-frequency signal transmitter with: a first strip line ( 10 ) on the surface of a dielectric substrate ( 11 ) for producing a signal; a second strip line ( 16 ) in the dielectric substrate ( 11 ) for the coupling-out and/or coupling-in of a high-frequency signal; a first interfacial connection device ( 15 ) in the substrate ( 11 ) for producing a conductive connection between the first and second strip line ( 10; 16 ); a first solid surface ( 12 ) essentially parallel to the microstrip line ( 10 ) and serving as a lower boundary surface of the substrate ( 11 ) in the vertical direction for producing a shielding; a second solid surface ( 18 ) essentially parallel to the first solid surface ( 12 ) and disposed at least in the region above the second strip line ( 16 ) on the substrate ( 11 ) for producing a shielding; a coupling opening ( 17 ) in the second solid surface ( 18 ) for radiating high-frequency energy; a planar coupling device ( 19 ) above and essentially parallel to the coupling opening ( 17 ); and a second interfacial connection device ( 20 ) between the first solid surface ( 12 ) and the second solid surface ( 18 ), in the region adjacent to the first interfacial connection device ( 15 ).

PRIOR ART

The current invention relates to a high-frequency signal transmitter andin particular, to a high-frequency signal transmitter with a stripline-to-coplanar transition.

A known method for transmitting high-frequency signals, e.g. inmicrowave engineering, is to use aperture-coupled patch antennae. Theseare employed in antenna arrays, i.e. antenna arrangements with severalof these patch antennae, or as individual emitters and/or couplers.

FIG. 4 shows a conventional aperture- or slot-coupled patch antenna. Init, an antenna patch 19 is excited via a coupling slot 17 in a solidsurface 18, the coupling slot 17 in turn being supplied by means of asupply line 16 embedded in a buried plane. Underneath this plane 16 isanother solid surface 12, that is connect in an electrically conductivefashion via interfacial connections 20′ to the solid surface 18 providedwith the coupling opening 17. A design of this kind is distinguished bya high transmission bandwidth. Between the supply line 16 and thecoupling slot, there is usually a substrate 11 provided, in which thehigh-frequency energy of the signal to be transmitted or coupled into islinked to the slot or to the coupling opening 17. In microwave antennaarrangements or connections of this kind, the supply line 16 embedded inthe substrate is usually provided in the form of a (triplate) stripline. The HF energy of the signal is conveyed between the strip line 16in the substrate and a solid surface 12, 18 on the top and bottom of thesubstrate.

But radiating the HF energy outward, e.g. into the air, from substrates11, is problematic, particularly when doing so from substrates that havea high dielectric constant. For example, if low temperature cofiredceramic (LTCC)—which is suitable as a base material for microwavecircuits—is used as the substrate material, then it becomes necessary tograpple with the problem mentioned above since LTCC has a quite highdielectric constant of ε_(r)>4. This results in a reduction in antennagain as well as a deterioration in antenna efficiency.

ADVANTAGES OF THE INVENTION

The high-frequency signal transmitter according to the invention, withthe features of claim 1, has the advantage over the known approach thatthe HF energy of the signal is concentrated in the region of thecoupling slot of the transmitter or antenna and there is an increase inthe antenna efficiency and antenna gain.

The idea underlying the current invention is essentially comprised inchanging over from a supply line produced using microstrip technology toa coplanar line via a microstrip-to-coplanar transition, the coplanarline being connected by means of an interfacial connection to the actualantenna supply line embedded in a substrate. This concentrates thesignal energy in the vicinity of the coupling opening of the antenna,which makes it possible to achieve an efficiency that is higher than ifthe microstrip line were to be directly connected to the supply lineembedded in the substrate by means of an interfacial connection, forexample.

In other words, in order to improve the efficiency of the high-frequencysignal transmitter according to the current invention, it is providedwith a device with a first strip line on the surface of a dielectricsubstrate for producing a signal, a second strip line in the dielectricsubstrate for the coupling-out and/or coupling-in of a high-frequencysignal, a first interfacial connection device in the substrate forproducing a conductive connection between the first and second stripline, a first solid surface essentially parallel to the microstrip lineand serving as a lower boundary surface of the substrate in the verticaldirection for producing a shielding; a second solid surface essentiallyparallel to the first solid surface disposed at least in the regionabove the second strip line on the substrate for producing a shielding,a coupling opening in the second solid surface for radiatinghigh-frequency energy, a planar coupling device above and essentiallyparallel to the coupling opening, and a second interfacial connectiondevice between the first solid surface and the second solid surface, inthe vicinity of the first interfacial connection device.

The dependent claims contain advantageous modifications and improvementsof the high-frequency signal transmitter disclosed in claim 1.

According to a preferred modification, the substrate contains a ceramicmaterial, preferably low temperature cofired ceramic (LTCC). Ceramicsubstrates and especially those made of LTCC have the advantage ofpossessing favorable high-frequency properties.

According to another preferred modification, the substrate has a highdielectric constant, in particular one greater than 4. This permits theselection of advantageous substrate materials.

According to another preferred modification, the second interfacialconnection device has a number of discrete interfacial connectionelements. This has the advantage of assuring the most homogeneous anduniform field transition possible in the transition region between themicrostrip line and the coplanar line from the lower, first solidsurface to the upper, second solid surface.

According to another preferred modification, the discrete interfacialconnection elements in the region of the first interfacial connectiondevice are arranged in a funnel-shaped pattern when viewed perpendicularto the second solid surface; the second solid surface also has afunnel-shaped recess in this region. This measure also promotes theuniform field transition in the region of the changeover from themicrostrip line to the coplanar line.

According to another preferred modification, the first strip linetransitions into a coplanar line in the vicinity of the firstinterfacial connection. This is advantageous since in this way, inconnection with the two features mentioned above, a majority of the HFenergy is no longer conveyed only between the strip line and the lower,first solid surface and consequently, can be better coupled out from thesubstrate in comparison to a device in which the supplying microstripline is connected to the line embedded in the substrate merely by meansof an interfacial connection (via).

According to another preferred modification, the second strip line isspaced a smaller distance away from the second solid surface than it isfrom the first solid surface. This brings to the given antennaarrangement the advantages of an asymmetrical triplate strip line.

According to another preferred modification, one end of the second stripline in the longitudinal direction is spaced apart from the couplingopening by approximately one fourth the wavelength of the useful signalwave on the strip line. This advantageously optimizes the coupling-outof the high-frequency signal through the coupling opening.

DRAWINGS

Exemplary embodiments of the invention are shown in the drawings andwill be explained in detail in the subsequent description.

FIG. 1 is a schematic oblique view to illustrate an embodiment of thehigh-frequency signal transmitter according to the invention;

FIG. 2 is a schematic longitudinal section to illustrate the embodimentaccording to FIG. 1;

FIG. 3 is a schematic detail viewed from above to illustrate theembodiment of the current invention according to FIG. 1 and FIG. 2; and

FIG. 4 is a schematic oblique view of a conventional high-frequencysignal transmitter.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Components that are the same or function in the same manner are providedwith the same reference numerals in the figures.

FIG. 1 is a schematic oblique view to illustrate an embodiment of thehigh-frequency signal transmitter according to the invention.

In FIG. 1, a first microstrip line 10 is shown, which is disposed on adielectric substrate 11, preferably comprised of a ceramic material suchas low temperature cofired ceramic (LTCC). Viewed in the verticaldirection, a first solid surface 12 preferably constitutes a lowerboundary plane of the dielectric substrate 11 and is electricallyconductive, preferably comprised of a metal. In a transition region 13from the strip line 10 to a coplanar line 14 on the surface of thesubstrate 11, the supply line 10, 14 undergoes a structural change.

The coplanar line 14 is connected by means of a first interfacialconnection device 15 to a second strip line 16, which is embedded in thesubstrate 11. The embedded strip line 16 preferably extends parallel tothe first strip line and likewise parallel to the first solid surface12. The interfacial connection device 15 between the coplanar line 14and the embedded strip line 16 is electrically conductive and preferablycontains a metal; this interfacial connection device 15 preferablyextends perpendicularly. The free end 16′ of the embedded strip line 16is disposed in the vicinity of a coupling opening 17 or coupling slot,which is disposed in a second solid surface 18 on the surface of thesubstrate 11, essentially parallel to the first solid surface 12. Abovethe coupling opening 17, essentially parallel to the second solidsurface 18, a coupling device is provided, preferably an antenna patchelement 19, which is electromagnetically coupled to the embedded line 16via the coupling opening 17. The coupling slot 17 is alignedperpendicular to the line 16 in a cross-like fashion, above which thepreferably rectangular patch element extends with its edges alignedparallel to this cross.

The second solid surface 18 is connected to the first solid surface 12in an electrically conductive fashion by means of an interfacialconnection device 20 that is preferably comprised of a number ofdiscrete interfacial connection elements 20′. The second solid surface18 preferably extends in the longitudinal direction parallel to thestrip line 10, 16 beyond the span of the patch antenna element 19 and inthe other direction, beyond the transition region 13 between the stripline 10 and the coplanar line 14. In the vicinity of this transition 13,the second solid surface 18 has a preferably funnel-shaped indentationor a funnel-shaped recess and encompasses the transition 13, thecoplanar line 14, and the region of the interfacial connection 15,without electrically contacting the respective devices.

The discrete interfacial connection elements 20′ between the first solidsurface 12 and the second solid surface 18 are preferably also arrangedin a funnel-shaped pattern, which approximately corresponds to the formof the funnel-shaped indentation in the second solid surface 18. Forexample, a discrete contacting element 20′ is round and cylindrical andis provided extending perpendicularly between the first solid surface 12and the second solid surface 18. In addition, the interfacial connectiondevice 20 between the solid surfaces 12, 18 is preferably mirrorsymmetrical to an imaginary plane of reflection extending through thecenter of the strip line 10 and the coplanar line 14. It would also beconceivable to provide a continuous, electrically conductive wall as acontacting device 20 between the solid surfaces 12 and 18, which wallcould extend, for example, along the contacting elements 20′ for whichit would then substitute.

FIG. 2 is a schematic longitudinal section to illustrate the embodimentaccording to FIG. 1.

FIG. 2 shows a longitudinal section along the center of the strip line10 and the coplanar line 14. A strip line 10 is provided on thesubstrate 11 and transitions in a transition region 13 to the coplanarline 14. This coplanar line 14 is connected via an electricallyconductive interfacial connection 15 to a strip line 16 that is embeddedin the substrate 11 and extends parallel to the strip line 10 andparallel to a first solid surface 12. The coplanar line 14 ends and thestrip line 16 begins in the vicinity of the interfacial connectiondevice 15 between the coplanar line 14 and the strip line 16. At theother end section 16′ of the strip line 16, a second solid surface 18with a coupling opening 17 is disposed on the surface of the substrate11 in the same plane as the first strip line 10.

The distance between the coupling opening 17 and the end 16′ of theembedded strip line 16 in the longitudinal direction, i.e. viewed in thedirection of the strip line 16, is preferably approximately one fourththe wavelength of high-frequency signal to be transmitted via the supplyline 10, 13, 14, 15, and 16. At a distance of λ/4 of the signalwavelength between the end 16′ of the strip line 16 and the opening 17in the solid surface 18, a maximal coupling occurs as well as a maximalexcitation of the planar emitter 19 or the coupling device.

The interfacial connection device 20 between the first solid surface 12and the second solid surface 18 is only shown by way of example in FIG.2 in order to demonstrate an existing connection between the twosurfaces 18 and 12 (a correspondence to a comparable location in FIG. 1is not shown). Although the first solid surface 12 appears to establisha boundary of the substrate 11 toward the bottom, i.e. in the verticaldirection, it is entirely possible for the substrate 11 to also continueon below the solid surface 12 and for the whole design or structure tobe multi-layered.

FIG. 3 is a schematic detail viewed from above to illustrate theembodiment of the current invention according to FIG. 1 and FIG. 2.

FIG. 3 primarily shows the transition 13 from the strip line 10 on thesurface of the substrate into the coplanar line 14 on the surface of thesubstrate 11. This transition 13, which preferably extends conically, ispreferably provided in a funnel-shaped slot or a funnel-shaped recess inthe second solid surface 18, which is connected to the first solidsurface 12, not shown in FIG. 3, via the interfacial connection device20 or the discrete interfacial connection elements 20′. The interfacialconnection elements 20′, which are preferably disposedmirror-symmetrical to the coplanar line and strip line 10, are alsoarranged in a funnel-shaped pattern.

If a change from a microstrip line 10 to a coplanar line 14 by means ofthe transition 13 occurs in the manner shown in FIGS. 1 to 3 before theinterfacial connection 15 into the embedded plane 16, then the HF energyis conveyed predominantly in the slot of the coplanar line 14. As aresult, after the interfacial connection 15 into the embedded line 16,with the asymmetrical strip line used here, the HF energy is conveyedchiefly between the upper solid surface 18 (with the coupling slot 17)and the embedded line 16. Consequently, the HF energy can be more easilycoupled out through the coupling slot 17 and there is an increase in theantenna efficiency and antenna gain. The interposition of the coplanartransition 10, 13, 14 improves the functioning of the antenna primarilybecause the reference mass for the HF signal can extend from the lowersolid surface 12 to the upper solid surface 18 without a discontinuoustransition. This prevents the HF energy from remaining in the substrate11 and being impossible to radiate.

Although the current invention has been explained above in conjunctionwith preferred exemplary embodiments, it is not limited to these, butcan be modified in numerous ways.

In particular, materials such as the ceramic substrate material LTCCshould be viewed as mere examples. Moreover, the above-mentionedfunnel-shape of the recess in the second solid surface in the vicinityof the transition between the strip line and the coplanar line shouldalso be viewed as an example; it is also conceivable to provide atransition that is round when viewed from above.

1. A high-frequency signal transmitter with: a first strip line (10) onthe surface of a dielectric substrate (11) for producing a signal; asecond strip line (16) in the dielectric substrate (11) for thecoupling-out and/or coupling-in of a high-frequency signal; a firstinterfacial connection device (15) in the substrate (11) for producing aconductive connection between the first and second strip line (10; 16);a first solid surface (12) essentially parallel to the microstrip line(10) and serving as a lower boundary surface of the substrate (11) inthe vertical direction for producing a shielding; a second solid surface(18) essentially parallel to the first solid surface (12) and disposedat least in the region above the second strip line (16) on the substrate(11) for producing a shielding; a coupling opening (17) in the secondsolid surface (18) for radiating high-frequency energy; a planarcoupling device (19) above and essentially parallel to the couplingopening (17); and a second interfacial connection device (20) betweenthe first solid surface (12) and the second solid surface (18), in theregion adjacent to the first interfacial connection device (15).
 2. Thedevice according to claim 1, characterized in that the substrate (11)contains a ceramic material, preferably low temperature cofired ceramic(LTCC).
 3. The device according to claim 1, characterized in that thesubstrate (11) has a high dielectric constant, in particular one greaterthan
 4. 4. The device according to claim 1, characterized in that thefirst strip line (10) transitions into a coplanar line (14) in thevicinity of the first interfacial connection (15).
 5. The deviceaccording to claim 1, characterized in that the second interfacialconnection device (20) has a number of discrete interfacial connectionelements (20′).
 6. The device according to claim 5, characterized inthat the discrete interfacial connection elements (20′) in the vicinityof the first interfacial connection device (15) are arranged in afunnel-shaped pattern when viewed perpendicular to the second solidsurface (18), wherein the second solid surface (18) also has afunnel-shaped recess in this region.
 7. The device according to claim 1,characterized in that adjacent to the first interfacial connection (15),the first strip line (10) is encompassed by the second solid surface(18), without contacting it.
 8. The device according to claim 1,characterized in that the second strip line (16) is spaced a smallerdistance away from the second solid surface (18) than it is from thefirst solid surface (12).
 9. The device according to claim 1,characterized in that one end (16′) of the second strip line (16) in thelongitudinal direction is spaced apart from the coupling opening (17) byapproximately one fourth the wavelength of the useful signal wave on thestrip line.